Bill Bagwell differential tempering

C

Casey Conley

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Oct 25, 2022
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I just got done watching a YouTube video featuring Mr. Bagwell and he states his blades have 4 different hardnesses to them. A completely soft tang with a spring tempered spine gradually going down to an optimally hardened edge and a slightly harder tip.
My question is: does anybody know the "European method" he's speaking of and how would I go about attempting this on a knife I'm making? Here's the link to the video in question.
He starts talking about the temper right around 3:20
Any helpful tips would be much appreciated
 
That european method dates back centuries, when steel overall quality was quite bad and weapons/tools rarely exceeded 50hrc. Most popular, at a time, was quenching right after the blade reached temperature and spine was still colder, therefore cutting edge was quenched but spine was soft. European method, was to soak all blade to uniform temperature, then quench, and then temper the blade with various temperatures, resulting in various hrc numbers and spine not only softer than cutting edge, but springy also. Sorry, if my english is bad. There is example how to temper (start at 7:30 in video)
 
Another European way is to harden all, stick the blade in wet sand and place hot charcoal around the spine and tang sticking above the sand. Grooves on a sword were used as charcoal placement to make the middle soft and edges hard. With a little imagination there are more ways of doing it. For example today one can use low frequency induction to locally heat and temper. Doesn't work with high frequency.
 
Another method of adjusting hardness was using a block of iron. Heat the block red and hold it against areas you wanted to temper down the hardness or rub the blade against the block. The block was often stuck down in the coals with just the top surface sticking up.
Using a glowing coal held in tongs was the same basic method with a more precise zone tempering, as would be used for the center of a double-edged sword.

IIRC, the European method has no tempering phase after the hardening like we do where the whole knife is tempered. The knife is quick tempered with direct heat to "draw the temper" as desired. The colors on the blade told the temperature and it was quenched to cool it when the color ran to the portion desired. Straw color was for the edge. Blue temper (spring temper) was for the spine. The tang was often stuck back in the coals and heated red and then slow cooled to completely anneal it.
As said by Lynx85, this was used in the days of lower grade steel and much softer knives and swords. With modern steels and precise temperature-controlled ovens we have no reason to do these types of tempering. After normal tempering to the desired edge hardness, you can draw down the spine and tang with a small torch. Metallurgically it is better to fully harden the blade and them fully temper it first.
 
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Wow. I always wondered how olde time smiths tempered their blades and never expected such a clear and concise answer. Fascinating.
 
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